I would think the most likely executive action (if any is taken) would be to instruct the DOJ and ATF to more strongly pursue "AW" sales and possession of items which the USSC ruled as AW under the Clinton AW ban. I don't seem to recall the USSC specifically overturning that ruling, and if they haven't, he would have a "constitutional leg to stand on".
"The existence of life is a highly overrated phenomenon."
-- Dr Manhattan
quis custodiet ipsos custodes